March 28 issue - The signs of a new threat in northern Virginiaemerged ominously in blood-spattered urban streets and rural scrub.Two summers ago the body of a young woman who had informed against herformer gang associates was found on the banks of the Shenandoah River,repeatedly stabbed and her head nearly severed. Last May inAlexandria, gang members armed with machetes hacked away at a memberof the South Side Locos, slicing off some of his fingers and leavingothers dangling by a shred of skin. Only a week later in Herndon, amember of the 18th Street gang was pumped full of .38-caliber bullets,while his female companion, who tried to flee, was shot in the back.The assailant, according to a witness, had a large tattoo emblazonedon his forehead. It read MS, for Mara Salvatrucha, the gang allegedlyresponsible for all these attacks.

At the nearby headquarters of the Federal Bureau of Investigation,agents—many of whom live in these communities—fielded the reports withmounting alarm. But Mara Salvatrucha, or MS-13, wasn't terrifying justnorthern Virginia. "They were popping up everywhere," says ChrisSwecker, assistant director of the FBI's criminal investigativedivision. "It seemed like we were hearing more and more about MS-13."Then one day last fall, FBI Director Robert Mueller called Sweckerinto his office. "You have a mandate to go out and address this gang,"Mueller told him. Mueller declared MS-13 the top priority of thebureau's criminal-enterprise branch—which targets organized crime—andauthorized the creation of a new national task force to combat it. Thetask force, which includes agencies like the Drug EnforcementAdministration (DEA) and Immigration and Customs Enforcement (ICE),aims to take on MS-13 much as the FBI once tackled the Mafia.

Composed of mostly Salvadorans and other Central Americans—many ofthem undocumented—the gang has a uniquely international profile, withan estimated 8,000 to 10,000 members in 33 states in the United States(out of more than 700,000 gang members overall), and tens of thousandsmore in Central America. It's considered the fastest-growing, mostviolent and least understood of the nation's street gangs—in partbecause U.S. law enforcement has not been watching as closely as itmight have. As authorities have focused their attention on the waragainst terrorism, MS-13 has proliferated. In the FBI's D.C. fieldoffice, the number of agents dedicated to gang investigations declinedby 50 percent. "There was a definite shift in resources post-9/11toward terrorism," says Michael Mason, assistant director in charge ofthat office. "As a result, we had fewer resources to focus on gangs,"though he adds that the bureau made up for any shortfall by leveragingresources from other agencies. In recent weeks, authorities have madestrides against MS-13: a gang leader accused of orchestrating aDecember bus bombing in Honduras that killed 28 people was arrested inTexas in February, and a recent seven-city sweep by ICE netted morethan 100 reputed MS-13 members. But Robert Clifford, head of the newnational task force, says "no single law-enforcement action is reallygoing to deal the type of blow" necessary to dismantle the gang. Noone is more interested in busting up MS-13 than leaders of the Latinocommunity, who live with the fear and fallout of the gang's savageactions.

MS-13 got started in Los Angeles in the 1980s by Salvadorans fleeing acivil war. Many of the kids grew up surrounded by violence. DelHendrixson of Bajito Onda, a gang-outreach program, remembers an MS-13member who recounted one of his earliest memories: guarding thefamily's crops at the age of 4, armed with a machete, alone at night.When he and others reached the mean streets of the L.A. ghetto,Mexican gangs preyed on them. The newcomers' response: to bandtogether in a mara, or "posse," composed of salvatruchas, or"street-tough Salvadorans" (the "13" is a gang number associated withsouthern California). Over time, the gang's ranks grew, adding formerparamilitaries with weapons training and a taste for atrocity. MS-13eventually adopted a variety of rackets, from extortion to drugtrafficking. When law enforcement cracked down and deported planeloadsof members, the deportees quickly created MS-13 outposts in ElSalvador and neighboring countries like Honduras and Guatemala.

Flush with new recruits from Central America, whether fleeing the lawor accompanying parents seeking work along the immigrant trail, MS-13members have set up cliques—geographically defined subgroups—in suchremote redoubts as Boise, Idaho, and Omaha, Neb. In these newsettings, gang culture often morphs. "Everything gets bastardized asit leaves the center," says Wes McBride, president of the CaliforniaGang Investigators Association. While machete attacks might occur onthe East Coast, they're rare on the West Coast. While car thefts anddrug trafficking might be big in North Carolina, gang-on-gang violencepredominates in Virginia. It's that decentralized nature of MS-13—withno clear hierarchy or structure—that makes it so vexing toauthorities. "Taking out the heart of the leadership is very hard ifthere is no definitive leadership," says one federal law-enforcementofficial.

But that could be changing. According to a 2004 report by the NationalDrug Intelligence Center, the gang "may be increasing its coordinationwith MS-13 chapters in Los Angeles, Washington, D.C./NorthernVirginia, and New York City, possibly signaling an attempt to build anational command structure." One potential illustration of such aneffort: on New York's Long Island last year, an MS-13 honcho arrivedfrom the West Coast "to try to organize these various cliques or setsinto a more formal structure," says Robert Hart, supervisory specialagent with the FBI. "That's a significant step in the development ofMS-13." And in northern Virginia, U.S. Attorney Paul McNulty observesthat "in some of the violent crimes, there seems to be a kind ofapproval process in some kind of hierarchy beyond the clique."

If MS-13 is seeking to create a national command in the United States,it would be emulating its model in El Salvador. There, says OscarBonilla, director of the National Council for Public Security, thegang is "highly organized and disciplined ... with semi-clandestinestructures and vertical commands." As a result, its criminaloperations are all the more efficient and pervasive. Theadministration of President Tony Saca has responded with a super manodura ("super hard hand") policy, reforming the penal code tofacilitate gang prosecutions. "We're not dealing with Boy Scouts orbums," Saca told NEWSWEEK. "We're dealing with true assassins, rapists."

In the United States, Clifford's new national task force, which willbe housed at FBI headquarters, is preparing a hard hand of its own.Serving as a national repository for MS-13 intelligence, it will helpdiscern trends, prioritize targets and diagram whatever leadershipstructure might exist. There's an international dimension, too: U.S.investigators will be exchanging information—such as a gang member'smovements and associates—with their counterparts in Central America.FBI agents sitting in regional U.S. embassies will serve as liaisonswith local authorities, and Salvadoran advisers will come to theUnited States to share their MS-13 expertise. All of which amounts to"a comprehensive international attack against MS-13," says Clifford.

But some kinks remain. In the recent sweep conducted by ICE, theagency nabbed a gang member whom the FBI was intensely interested in."This was not somebody we were ready to scoop up," says a federallaw-enforcement official, who complains that ICE didn't alert otheragencies of its impending raid. (An ICE spokeswoman insists that alltargets were cleared with other agencies. Another ICE officialgrumbles that "the bureau thinks it has jurisdiction overeverything.") Meanwhile, down in El Salvador, officials fear therepercussions of another batch of MS-13 deportees heading their way."Those deportations are a time bomb," says Bonilla. "When a gangmember is deported from the United States, it destroys in one monthwhat we've achieved in a year of [gang-prevention work]." Forauthorities to succeed in this war, they'll need to cooperate at leastas well as the gang they're trying to wipe out.

With Daren Briscoe, Daniel Klaidman and Michael Isikoff in Washington,Jennifer Ordonez in Los Angeles, Joseph Contreras in Miami and AlvaroCruz in San Salvador